German Laid-Open Document DE 100 02 457 describes a sliding roof system that employs two straight guide tracks extending roughly in the longitudinal direction of a vehicle along the roof. The distance between the guide tracks decreases from front to back. To guide the cover in the tracks, two guide elements are provided, each of which is contained in one of the guide tracks and connected to the cover by a parallelogram guide. This makes it possible for the distance between the two guide elements to change as the distance between the guide tracks changes.
In theory, the two parallelogram guides would also prevent the cover from twisting about its vertical axis or from being laterally displaced. In practice, however, the cover is prevented from twisting and displacement due to the guide elements precisely guided in the guide tracks and due to the cover being prevented from tilting. In other words, every force acting upon the cover to displace it laterally or to twist it about its vertical axis leads, as a result of the parallelogram guides, to rotational forces being applied to the two guide elements in the guide tracks. As a result, the entire sliding roof system is relatively hard to move and tends to jam. In addition, the parallelogram guide is only suitable for straight-line guide tracks that lie parallel to each other, not guide tracks whose distance from each other varies along the length of the track.
There is a desire to refine a sliding roof system to support the cover in a centered position relative to the guide tracks without risking the possibility that the guide elements may jam in the guide tracks or that the entire system may be subjected to undue strain.